var a = {}
a["name"] = "feng"
a["age"] = 18
a["sax"] = true

// console.log(a)
for(item in a){
    // console.log(item)
    // console.log(Object.prototype.toString.call(item));
    // console.log(a[item])
    // console.log(Object.prototype.toString.call(a[item]));
}
console.log(Object.keys(a));//遍历数组就是index

var b = '{ "name": "feng", "age": 18, "sax": true }'
// console.log(Object.prototype.toString.call(b));
var b = JSON.parse(b)
// console.log(b)
// console.log(Object.prototype.toString.call(b));
var c = JSON.stringify(b)
// console.log(b)
var d = { name: "feng", "age": 18, "sax": true }
// JSON.stringify(d)
// console.log(d)
// console.log(Object.prototype.toString.call(d));
var f = [1,3,2,3,4,5]
for(var i =0 ;len= f.length,i<len;i++){
    // console.log(f[i]);
    console.log(len)
}
console.log(len)